Meter to measure and print-out the ratio of a measured parameter to a calibrated standard value



July 25, 1967 Original Fil ed Feb. 17, 1961 UNIT UNDER TEsT UNIT UNDERMETER TO MEASURE AND PRINT-OUT THE RATIO OF A MEASURED PARAMETER TO ACALIBRATED STANDARD VALUE 2 Sheets Sheet TEST 2| 22 23 FIG Z l.

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METER TO MEASURE AND PRINT-OUT THE RATIO OF, A MEASURED PARAMETER TO ACALIBRATED STANDARD VALUE Original Filed Feb. 1.7, 1961 I 2 Sheets-Sheet2 SOLENOID 77,

ATTORN EY United States Patent 3,333,194 METER T0 MEASURE AND PRINT-OUTTHE RATIO OF A MEASURED PARAMETER TO A CALIBRATED STANDARD VALUE RalphReynolds Batcher, 24002 42nd Ave., Douglaston, N.Y. 11363 Continuationof abandoned application Ser. No. 89,953, Feb. 17, 1961. Thisapplication Aug. 11, 1965, Ser. No. 478,957

1 Claim. (Cl. 324-158) This invention relates to a measuring andindicating instrument and system assembly to also constitute a printoutrecorder, and consisting of an instrument assembly for measuring anelectrical quantity and for then displaying or recording the resultinginformation in a dorm suitable for rapid processing.

This application is a continuation of my application Ser. No. 89,953filed Feb. 17, 1961, entitled, Measuring and Recording Instrument, nowabandoned.

In many industrial operations, measurements are made of one or moreconditions involved in or relating to the operation, since the levels orvalues or attributes of those operations may change, and a knowledge orrecord of the nature and extent of such changes may be wanted or needed.Such measurements are made at frequent intervals, so variations from adesired average value can be readily and quickly ascertained to serve asa guide for desired control or regulation.

Indeed, in many manufacturing processes, periodic or spot samplingmeasurements have given way to a policy of a complete 100% check on allitems produced. In such cases, it is often desired that suchmeasurements be recorded as information for -urther assistance orguidance to the makers or users of those items. Such information may hewanted to permit grading the items according to the values of certainparameters, or according to the deviation of the parameters from adesired standard or mean value.

- A great many of these measurements are made by noting electricalcurrent values established by the eifects of each item in a standardcircuit. Quality control checks on electron tubes, on transistors,resistors, etc., are examples of such procedure. In other cases,measurements of temperatures, pressures, flow rates or other quantitiesof a non-electrical nature can be converted to equivalent electricalcurrent values.

Where the operator may be more concerned with the deviations from thedesired mean value than he is with the absolute value, it is desirablethat readings be made and that records be kept in terms of percentagevariations rtrom the desired mean. The making of such measurements,their recording and their conversion to percentile values must be doneat speeds that will not slow down the production procedure. Productionspeeds in manufacturing the above products, and many others, are at highrates, so that measurements should be fully automatrc as far aspossible.

This invention is directed to an instrument and system assembly formeasuring quantities and the deviation of suchquantities from thedesired mean setup as an arbitrary or selected standard value, and fordirectly computing the deviation in percentage terms as a percentileratio to the standard value. I

This invention utilizes an instrument assembly that will take note ofthe electrical current levels at some point in a test circuit as theproduct items are rapidly connected .to such circuit in consecutiveorder. The instrument assembly will then compare each reading with aselected predetermined mean or' average value, and will then displayeach measurement in terms of the percentile ratio of the average value,either visually to the operator, or as a printed record that can benoted later.

"ice

F or the instrument to be universally applicable to the varlety of teststhat are to be made in such applications, it is necessary that the levelof a selected median value in the instrument be established precisely ata selected point within a permitted wide range of values at whichmeasurements might be needed over a period of time. For example. suchmedian values might be established at any point between a fewmicro-amperes and many amperes, during the course of testing electrontubes or transistors. This invention provides an instrument that permitsthe median value to be established in a very simple manner that does notrequire skilled operators to make changes in the setting of such medianreference point or value.

The instrumental employed in this invention comprises an electricalcurrent-sensitive meter-relay having a precise- 1y established designoperating point. This design operating point may be selectively andadjustably recalibrated, at the will of an operator, by external shuntsor resistors, .to cause the meter relay to measure some other selectedindicated current value, and to operate at such apparent value.

For the purpose of this invention, a series of resistors is providedthat are arranged for easy and simple assembly into a desired shunt andseries network in circuit with the operating coil of the meter relay toestablish a desired new calibration or arbitrary standard value forcomparison. A feature of the invention is the use of a punched card forselectively connecting appropriate resistors in the network circuit toachieve the desired new calibration 02E the meter operating coil.

'That calibration, by resistors of fixed values may, for convenience, betermed a passive or static calibration, as distinguished from anadditional variable calibration to be later added, which will be, ineifect, a dynamic calibration.

That new passive or static calibration may obviously be modified tocause the meter to be further calibrated by the insertion of addedresistance in the coil circuit. If such added resistance is fixed, themodified calibration will also be passive or fixed. If, however, suchadded resistance is variable, the modified calibration can be variedaccording to the eifect of the variation of the resistance value in thecoil circuit. If the variable resistance is varied quickly throughoutits range of values during a short test interval, the modifiedcalibration of the meter becomes a dynamic calibration.

A primary purpose of this invention is to provide a system in which suchstatic calibration and such dynamic calibration may be established, toenable selected parameters of tested devices to be readily and quicklymeasured and compared with a standard value.

Without any external calibrations, the meter relay will have a preciseoperating point, requiring a specific value of operating current. Inadjusting the meter to a new desired static calibration, by externalresistors, the equivalent or apparent operating point of the meter willapparently be changed, according to that calibration. However, thecurrent actually required to flow through the meter element to operatethe relay switch will remain the same.

If, however, in addition to such static calibration, an additionalvariable or dynamic calibration is provided for the meter relay, byincluding a dynamically variable resistor, an equivalent or apparent newoperating point of the relay may be established and shifted throughout arange dependent upon the relationship of the added variable resistor tothe total effective resistance in the circuit of the meter coil. Thisrelationship will be explained in more detail in connection with thedrawings.

For the purpose of this invention, a static calibration point will belocated at an intermediate or mid-point of the dynamic range. Thatcalibration point will represent 3 unity or 100% standard value of theparemeter under investigation.

Each product item under test will have its own characteristics, whichwill determine the value or level of the parameter being investigated.By suitable means, that parameter may be converted to a correspondingcharacteristic voltage or current which may be readily measured. Thatcharacteristic voltage or current may then be increased or decreased, asmay be necessary, until it provides the components of current equal tothe value of operating current needed to operate the relay switch.

When such characteristic current in the item under test corresponds tothe calibration value which provides the component of current to equalthe meter operating current value, the meter switch will be operated.That operation will control the provided external circuit to operate anindicator or a display device, or to operate a recorder to record theparameter value, or, as arranged in this invention, to record the ratioof the tested parameter value to the predetermined unity or standardparameter value corresponding to the arbitrary unity or standard set upfor unity comparison. I Thus, in accordance with this invention, a meterrelay having a specific precise designed operating point, to operate aswitch, is calibrated by a set of selected fixed resistors to establisha static calibration point, as a unity standard of measurement, within arange through which the meter element may be further dynamicallycalibrated by a scanning or swinging variation of a variable resistor,to test and'measure an external variable condition and to compare thevalue or measure of that condition with said pre-determined value set upas a unity standard of value for such comparison.

The invention utilizes the meter relay, a set of fixed resistors whichmay be selected for connection to the meter coil to establish a desiredcalibration, and a recording mechanism which is controlled by arotatable printing disc that is co-axially disposed and rotatable withthe variable resistor. During the scanning operation, the variableresistor will adjust to a value which will cause operation of the meterrel-ay. That value of the variable resistor will represent thecalibration of the meter relay corresponding to the value of theparameter of the item or unit being tested. The meter relay will thusoperate the switch to cause the recording mechanism to operate at acorresponding position of the printing disc.

By way of example, the recording mechanism shown herein is itselfcalibrated in percentile ratios, so the value of the tested parameterwill be recorded as a ratio relative to the preset unity standard.

The manner in which the invention is constructed and operates isexplained in detail in the following specification in connection withthe drawings, in which FIGURES 1 to 5 are simple schematic diagrams ofa'meter relay coil circuit in various stages of calibration;

FIGURE 6 is a schematic perspective view of an indicating form of theinvention;

FIGURE 7 is a schematic perspective and diagram of a recording form ofthe invention; and

FIGURE 8 is a diagram of the control circuitry for the apparatus. InFIGURE 1, a relay 20 is connected in a meter circuit 21 connected to atest circuit 22 including a unit 23 to be tested for a parameter thatmay be measured by the current through the unit. The relay 20 isprovided with a switch 24 which will be operated when the relay coil isenergized by more than a precise value of current. The relay 20 is hereillustrated as an ordinary relay, but, for the sensitivity and accuracydesired for this application, the relay will be of a meter or instrumenttype. The switch may be either normally closed or normally open. Forthis application, the switch is normally open and closes when the coilis energized at its operating value. The switch controls an externalcircuit to an indicator or recording device or system as describedlater.

In the circuit of FIGURE 1, the current in the coil circuit 21 is thesame as in the test circuit 22. The calibration ratio is one-to-one andthe calibration constant is one (1). The meter coil therefore reads thetest unit current directly. Assuming the meter coil operates at oneampere, the current in the tested unit will be one ampere when the relayoperates. The parameter being measured in the tested unit will be of avalue corresponding to a current of one ampere through the tested unit23.

For the purpose of the analysis of FIGURES l to 3, the tested unit 23will be assumed to have the exact or desired value of the parameterbeing used to qualify in this test.

In FIGURE 2, a shunt resistor 30 is connected across the meter circuit21. For convenient reference, the resistance of the relay coil is takenas Z and the resistance of shunt resistor 30 is taken as Z/X. Thecurrent in test circuit 22 is now subdivided through meter coil 20 andthrough shunt resistor 30 in inverse proportion to the impedance of themeter coil, as one circuit sub-division, and of the shunt resistor as asecond circuit sub-division, according to well-known rules of parallelcircuits. Assuming that meter coil impedance is Z and that the impedanceof resistor 30 is Z/4, that is, one-fourth the impedance of meter coil20, the coil circuit will receive only one-fifth of the current in thetest circuit 22. In order for the relay to operate at its characteristicvalue, the current in the test circuit 22 must now be five times thatvalue. The calibration ratio is five-to-one and the calibration constantis five (5).

It will be realized that with a current-shunting arrangement as inFIGURE 2, the calibration constant increases, or is larger, as more testcircuit current is diverted from the meter coil. Inversely, as lesscurrent is diverted from the meter coil, the calibration constantdecreases, or is smaller. The characteristic operating current value ofthe relay itself, however, remains always the same.

By providing a resistor in series with the relay coil, the relay may becontrolled to operate in response to a voltage in the test circuit thatwill cause the characteristic operating current to flow in the relaycoil. For a large voltage in the test circuit the series resistanceshould be larger. The minimum test voltage, to be efiective, must besufiicient to cause the characteristic operating current in the relaycoil without a resistor in circuit.

Thus, for any voltage within a selected range in the test circuit, aresistor of appropriate resistance value can be provided in the relaycoil circuit to cause the current in the relay coil to be thecharacteristic operating value. In order to measure the value of aselected parameter of an electrical component, a voltage can bedeveloped in the test circuit, that is related to such value of theparameter. That voltage can then be measured by the relay coil andindicated or recorded, or utilized in some desired way. In order to varythe voltage applied to the relay coil, a variable resistor 35 isdisposed in series with the relay coil 20, as shown in FIGURE 3. Eachsetting of the variable resistor elfectively changes the calibration ofthe relay, since some of the applied voltage is lost across theresistor. The resistance setting can be varied, as necessary, accordingto the voltage from the component being tested. The unknown parameter ofa component under test might have a value above, equal to, or below, thedesired value. To, ascertain its value, therefore, a comparison must bemade over a selectable range of possible values.

Here it is done over a range centering around the desired median value,which will correspond to of .the desired value. The range over which thesearch is made represents the dynamic calibration imposed on therelayand the establishment of the center of this range, at the desired medianvalue, represents the static calibration of the relay at said 100% valueof the parameter to be measured.

A range of values is established for the variable search resistance 35,of value Z1, in FIGURE 3, to define this desired search range that willinclude the selected parameter value of the median, and a prescribedrange of values above and below this median value. A dial 40 isassociated with and indicates the setting of search resistor 35, and canhave a linear scale. Dial scale 40 and search resistor 35 aremechanically interlocked to work together, and are rotated manually or'by a motor over a complete circle of rotation, during each test of acomponent.

One terminal of fixed value shunt resistor 30 is connected to a movablecontact 35-a of the search resistor 35. As the contact 35a is movedcontinuously over the entire resistor 35, the calibration of the systemis shifted from one extreme value to the other, through the preselectedrange.

Contact 35a is referred to as movable, for convenience of description.That contact could be stationary and the resistor 35 could be movable,since relative motion is the thing desired. In either case, the scale 40is supported with the movable element, as indicated by the dottedconnection 40-1: representing a shaft or common support.

During this rotation the point, or current value, at which the relay 20operates is evidenced by the movement of the contacts 24. In thefollowing analysis it will be assumed that these contacts are normallyclosed and are connected in a circuit, hereinafter described, thatfunctions to stop the movement of contact 35-a on the search resistor35, and its associated scale on marking dial 40, at that relay operatingpoint. This resistor contact 35-a must star-t its rotation at theparticular end of the resistor 35 that connects the maximum value of itsresistance in series with the meter winding. The current level,controlled by the component under test, will usually be insufficient topermit this meter to operate when this maximum amount of resistance isin the circuit. However, if the relay does operate at that time, thecomponent clearly exhibits resistance conditions at or below the lowerlimit of the range over which the tests are conducted, and the movementof the dial is stopped immediately and this low limit is so displayed.

When resistance conditions in the tested component are more nearly equalto the median, the current slowly builds up in the relay operatingwinding as the rotation of resistor 35 progresses, so that at some laterpoint relay 20 operates and contacts 24 open. At any such point of relayoperation, the dial 40 indicates the percentage ratio of parameter valueto unity. With a component under test that exhibits adherence to thedesired level precisely, the rotation will stop at the mid-point, or100% point on the scale 40. Similarly, one with higher-thannormal valuewill require still greater current to effect operation, so that therotation of the slider 35-a must be carried past center, entering thearea where dial 40- carries percentage marks that are above 100%.

The relay 20 in FIGS. 1 to 3, can be any regular relay, but for theaccuracy desired at small angular movements the relay is preferably ofthe instrument type, such as a dArsonval movement with a coil elementtorsional'ly suspended in an air gap of a magnetic field from apermanent magnet.

It is found, both from practice and theoretical considerations, that thescale 40 associated with the settings of the search resistor 35 islinear, that is, it has graduations with equidistant intervals whencalibrated in percentage values. However, if the shunt resistor 30 usedin any particular test is not substantially lower in resistance valuethan the resistance of coil 20 some non-linearity is possible.

This anomaly is avoided however in an alternate and sometimes preferablearrangement, shown in FIGURE 4. Here an auxiliary coil 41 is disposedand supported with the main coil 20 to be either differentially oradditively effective, when connected to control the effective flux fieldand consequently to alter the eflective torque and the operating currentto cause operation of the relay. This auxiliary coil can be energizedconveniently from a local source of voltage 47, such as a battery, astandard cell, a zener unit, or the like, through a limiting resistor48. The operating point of the relay is thus determined by both thevalue of the shunt circuit across coil 20 and the current applied to theauxiliary winding 41.

This double winding, which can conveniently consist of a single windingwith a center tap brought out, gives complete independence of the twowindings. Thus the connection to the search resistor 35 providing thedynamic calibration can be made in the circuit to the auxiliary winding41. This isolation avoids the effect of the variations in resistor 35from affecting the linearity of the system at high sensitivity settings,as mentioned heretofore. Thus, the scale 40 is linear and has constantaccuracy with any value of shunt resistance 30. An additional feature isthat a simple means is provided to change the percentage range overwhich a search is to be made.

In FIGURE 4, this meter relay mechanism need not have the usual heavyretractile springs that provides the counter-torque to the operatingtorque. The coils when unenergized may be substantially free floating.Positional bias, such as usually introduced by such a spring, isprovided herein by a definite fixed current in coil 41, to keep thecontact assembly 24 immobilized until the current from the test circuit,applied at terminals 22 and modified by the static calibration means 30,is applied to coil 20 at a sufiicient level to overcome the reverse biastorque from winding 41.

A multi-point range switch 43 is provided, that has two sections toalter two resistances 44 and 49, to provide for three different searchranges.

The action is best explained by a typical example based on the circuitin FIGURE 4. Assume each winding 20 and 41 to have one hundred (100)ohms resistance, and the basic sensitivity of the combination is suchthat operation occurs when coil 20 has ten microamperes flowing throughits turns. The current in coil 41 will also be of about the same value,the exact levels being determined by the off-center Weight of the movingcoils and by any residual spring action in the moving system present. Asmall trimmer resistance 42 can be used to establish this operatingpoint at say ten microamperes or some other value, precisely. Resistor42 slightly modifies the effect of a similar current from source 47flowing through coil 41. Ten microamperes through a winding resistanceof one hundred (100) ohms requires a potential of one millivolt to beavailable across points 38 and 39, when the slider 35-a is at themidpoint of resistor 35. Resistor 35 may conveniently be one ohm total.

Assume that the three search ranges desired are 50%, 20% and 10%, bothabove and below the median point of unity or 100%. These search rangesmay be selected by switch 43. The dial 40 would then have three scalesindicating search ranges of 50% to 150%; to 120% and to respectively.Assume that the voltage source 47 delivers 1.5 volts. Switch 43 has twoarms, one arm 43-a to connect to taps on resistor 44 having a totalresistance of 4.5 ohms, and the other arm 43-h to connect to taps on thetwo ohm resistance 49. The voltage drop across points 38 and 39 is equalto one millivolt when the slider of search resistor 35 is at its midpoint. The resistance of this lower half of resistor 35, namely one halfohm, represents 50%, 20%, or 10%, of the selected total resistance valuethat determines this. one millivolt drop, when the arm of switch 43 isat each of the three positions. The second arm of 43 acts tocompensatefor the change in the total voltage drop as the range is altered. Thesevalues are computed using usual resistance times current relationships.The large resistance 48 with its adustable section 48-a together providea drop of 1.499 volts if the voltage of 47 is exactly 1.5 volts.

Resistor 48-a can be used to compensate for changes in the output ofsource 47.

As in the previous circuits, the shunt resistor 30 will be adjusted toan appropriate value to establish the desired static calibration givingthe precise median value desired for the test. The meter sensitivity isthe same for all tests. In the above example it operates at tenmicroamperes, whereas an effective static calibration for a test mayhave some higher value within a considerable range. It is common toestablish this median value during a particular test at somenon-integral value, such as 460 microamperes or 7.21 milliamperes, orsome other odd value.

In the practical use of this system, therefore, a rather wide range ofvalues for a shunt resistor, indicated generally by numeral 30, will beneeded, and each particular value must be selectable quickly andprecisely. A useful arrangement from among the many that are commonlyused in changing the ranges of electrical instruments is shown in FIGURE5. Here a series resistor 51 and two groups of four shunt resistors 52to 55, inclusive, and 56 to 59, inclusive are provided. Based on thesame assumed one hundred (100) ohm resistance in winding 20, the valuesshown will boost the value of the operating point to any value within al000:1 range by manipulation of various of the nine contact switchesshown, to provide a resultant effective shunt 30 for the desiredcalibration multiplier. Thus, to obtain the above mentioned 460microampere setting, switches associated with resistors 52, 56 and 59would be closed. To obtain a median setting of 7.21 mil'liamperes,switches associated with resistors 51, 52, 53, 55 and 57 would beoperated. In usual practice, additional groups of four resistors andpossible additional series resistors could be added to extend the rangeof an instrument beyond the 100021 range provided here. This arrangementfor providing the variable shunt resistance 30 is particularly adaptedto selection by punched card control when applied to automatic testingtechniques.

An essential feature of this system is the provision of means fordisplaying the point of contact on the search resistor 35 at whichoperation occurs. If a visual indication of this value only, isrequired, the scale 40 may be stopped until an operator can note thereading, as in FIGURE 6. In other applications it may be desired toprint this value on a strip of paper or other record, or to punch holesin a tape in accordance with some selected binary code that representsthe noted value or again, to operate sorting gates for the properdisposal of each item tested, in accordance with ranges of values, intoproper bins, or to effective corrective measures to the productionprocess so as to bring about a greater percentage of the items fallingwithin close tolerance limits. It will be shown that all of theseeffects can be obtained, even simultaneously if desired.

The integral relation between the search resistor setting 35 and thescale 40, shown symbolically in FIGURE 3, can be effected directly, bymounting both on the the same drum 60, as in FIGURE 6. The drum 60,carrying scale 40 and its associated search resistor 35, is alsosupplied with gear-like teeth 62 on one edge of its periphery, with theteeth positionally related to the marking division of scale 40. Thisdrum 60 is driven by a light, lowtorque motor 70, at a convenient speed.The motor is one that can be stopped by stalling as by the movement of apawl 66 into one of the spaces between teeth. A spring driven rotatorcan alternately be used, where the power spring is partially wound upafter each reading is made.

In FIGURE 6, the pawl 66 is attached to the magnetic armature of anelectromagnet, and is normally held away from the gear teeth. Thiselectromagnet 64 is supplied with current from an external source, suchas the battery source 47 of FIGURE 4. It cannot pull its armature 67down, but can hold the armature down if it is once pushed 8 down againstthe pole faces. The current to this electromagnet however passes throughthe normally-closed contacts 24 of the relay 20, of FIGURE 4. Sincethese contacts open when the unknown point value has been found duringthe course of a revolution of the search resistor 35, the armature 67 ofthe electromagnet 64 will be released and fly up to engage a tooth ofthe gear and stop the rotation, permitting the reading to be made by theoperator. Thereafter a manual lever 61 may be depressed, so that a pin63 may restore the armature 67 against its pole pieces and permit thedrum 40 to continue to rotate until a stop pin 68 strikes an extensionstop 69 of this lever 61 at the start of a new revolution. When a newcomponent is put in place for testing, this lever 61 is depressed,disengaging the stops 68, 69 and letting the drum 40 start on a newsearch. At the start of a revolution, meter relay contacts 24 werereclosed, reenergizing 64 and keeping the armature 67 down. Each searchis thus under the control of the operating lever 61.

Another of the features herein can be added if the drum 40' isadditionally provided with a contact arm to pass over a series ofcontacts on a wafer switch during each revolution, these contacts beingdisposed so that they are adjacent to positions of the scalecorresponding to the sorting limits desired. A closure of a particularcontact of this series, upon stoppage of the drum 40, energizes acorresponding sorting gate operated by an electromagnet, or other gatingcontrols of a type used in automatic control operations.

In case a printed record is wanted, in addition to, or instead of, thevisual display, a new scale is embossed on the periphery of the drumalong with, or in place of, the display figures. The general details ofthe printing portion of the system that effects such printing operationare shown in FIGURE 7. It is often desirable to use such print-outmethods in automatic inspection processes, where a continuous stream ofcomponents to be tested are applied to the test circuit. There, stoppagefor reading scales. as in FIGURE 6, would be undesirable and theprinting must be done on the fly. An extremely sharp blow, such as canbe produced by a marking solenoid energized quickly, as by the dischargeof a capacitor, or a momentary closure of a power circuit will producesuch an impression without need for stopping the drum 40. Whilebasically the print-out, feature of FIGURE 7, is similar to the displayarrangement, of FIGURE 6, additional facilities will be needed forprint-out. The recording of the successive readings may be made on anyof several media, roll of paper, tag, or printed form. In the followingdiscussion of FIGURE 7, a paper strip 70 from a roll 71 will be assumedfor recording the succession of readings.

In FIGURE 7, a carriage 78 carries guides 79 and 80, which retain thepaper strip 70 in place, a marking platen 81, which forces this paperstrip 70 against embossed figures 82 on the periphery of the drum 40,and a pawl 83 that engages a ratchet 84 that is associated with papertape advance rollers 85. These rollers advance the tape a short intervalafter each printing operation. The carriage 78 swings through a smallarc around a hinge pin 86. An ink roller 73, of felt, or of othersuitable ink-absorbing material, carries marking ink and coats thesurface of the embossed figures 82 on the periphery of the drum, at eachrevolution of this drum. I

In usual operations the print-out facilities are used in automaticinspection processes, and a supplemental visual display is not requiredsince readings by an operator only slow down the test.

In testing, the only delay between readings is that which makes surethat a new item to be tested is in the circuit before a new scan isstarted.

Such procedure is accomplished as shownby the circuit in FIGURE 8containing the relays and 95. Upon the opening operation of meter relaycontacts 24, the relay 90 will be de-energized and its circuit held openby the opening of its contacts 90-a and 90-b. The drum 40 continues torotate around to the end of that revolution. A rest position switch 100associated with drum 40 at this rest position, causes operation of relay95, which operates however only after the meter relay contacts 24 havereclosed, since this relay 95 does not remain operated during thetransition between the end of one test and start of the next test.

At start of an operation, meter relay 20 is de-energized and its switch24 is in closed position. The drum 40 of FIGURE 7 will be in rest orstart position, at which rest position switch 100 will be closed. Inorder to start drum 40, the meter relay switch 24 should be closed andthe rest position switch 100 should be closed and a test control switch105'should be closed to indicate that a test unit is in place for thenext test. The circuit to relay 95 is closed through switches 24, 105and 100 to the supply source shown as battery 110. Relay 95 operates toopen its switch 95a to de-energize the drive motor 115 for the drum 40.To start the motor 115 the circuit to relay 95 should be openedmomentarily. That may be done at an auxiliary switch 116, as, forexample, by movement of the unit 23 to be tested as it moves into testposition to close switch 105. The momentary de-energization of relay 95permits its switch 95-a to close, thereby starting motor 115 and movingrest position switch 100 to open position, to open the circuit for relay95. Switches 105 and 116 should thereafter be closed before the end ofthe scanning cycle, so the subsequent reclosure of rest position switch100 will energize relay 95 to open the circuit to motor 115 and stop themotor until the next unit to be tested can be put in place.

At rest position, the operation of relay 95 opens switch 95a to open thecircuit to motor 115; closes front switch 95-b to close the energizingcircuit to relay 90 through meter relay switch 24, switch 95-b, relaycoil 90 to battery, and opens switch 95-c, to be referred to later.Relay 90 operates to close its back contacts 90-a and 90-b for a lock-incircuit through meter relay switch 24, to hold relay 90 operated eventhough relay 95 will be de-energized in a later operation.

As previously mentioned, the circuit to relay 95 is momentarily broken,and then held open by rest position switch 100 until the end of theensuing scan. Motor 115 operates the scan resistor arm 35-a and drum 40.At the instant of reading the parameter value of unit under test 23,relay meter switch 24 opens, and opens the circuit of relay coil 90.This permits two switches 90-a and 90-b to open. At this time relayswitch 95-b is open and 95-0 closed. Opening of switch contact 90-a,bridged by open switch contact 95-b, leaves relay 90 de-energized. Nowswitch contact 90-11, which is a make-before-break switch, firstmomentarily closes a circuit through back contact 95-c to solenoid 77 toactuate the marking platen 81 in FIGURE 7 to strike the paper to recordthe instantaneous value of the reading on the drum 40 at the instant themeter relay 20 opened its switch 24. The continuing movement of openingcontact 90-b then opens the circuit of solenoid 77.

The motor 115 continues until it rotates to rest position where itcloses switch 100. By this time meter relay switch 24 is closed andswitch 105 has been closed. Relay 95 is energized and disconnects themotor at switch contact 95-a. At the same time relay 95 opens contact95-c to prevent solenoid 77 from being energized when relay 90 isre-energized through contact 95-b.

The basic concepts heretofore described are primarily concerned withrapid inspection of product attributes, by utilizing a comparison scalewhere all divergences from a specific value are noted and are convertedto percentile values compared with such desired specific value as anaverage or mean value in a permitted range of deviations.

However, absolute value can equally well be displayed instead of suchpercentages, when specific rather than universal values are needed. Thescale 40 in the various 10 figures described could carry direct readingline voltage values, temperature readings, flow-rates or any otherprimary quantity found in a process. In practice such a quantity couldbe sampled at desired intervals, so that its level or value could beprinted out directly.

It is evident that several different drums of the type 40 of FIGURE 7could be driven by the same motor, and a paper tape sufficiently wide tohandle all readings side by side would provide what is known as amultiplepoint recorder in industry. Each drum would have its ownaccessories shown in FIGURE 7, except that only one tape advance ratchetwould be needed. Each drum scale could be related to measuring anentirely different effect in the process under examination.

Likewise, several different attributes of the same item under inspectioncould be measured simultaneously. Moreover, some of these could recorddirect values, and others the percentile values if desired. Suchrecordings in digital figures are obviously easier to analyze than theinterpreting of curves on circular or linear charts found with the usualmultiple point chart recorder. For such work it may be desirable totrigger off recordings at definite intervals, say every five minutes.Here use would be made of a master timer closing contacts 105 of FIGURE8.

When a plant control is centralized at a master control panel manydifferent factors can be recorded simultaneously at this centralposition, although the meter relay elements for the various quantitiesnoted might be at widely separated points, since the meter relay element20 and its own static calibration network 30 require only a two wireon-off signal circuit to couple it to the rest of its system, and thissignal circuit can be run quite a distance with suitable precautions.Because the relay 20 is usually sensitive to shock and vibrationeffects, it is usually mounted on vibration reducing absorbers away fromthe motor and solenoid which are shock-producing parts of the circuit.

As previously mentioned, it is also possible to adapt the principlesdescribed to apply corrective or control effects on the process, alongwith measurements of the value levels of some element in that process.Corrective measures can be applied in direct proportion to thedivergence of the measured attribute compared to the desired mean.

Referring to FIGURE 8 a typical circuit for the control of the scale 40is shown. It will be noted that the relay is in its non-operatedcondition for a duration equal to the deficiency of the attribute from amean level, this duration being considered in terms of the time requiredto make a whole revolution. Relay 90, using suitable auxiliary contacts,can be used to inject material, heat or whatever is needed to maintainthe proper level. The amount injected each revolution is thenproportional to the down time of this relay.

In some industrial control problems it is desirable to provide a recordof production factors or other values in a form that can be applieddirectly to computers or other analyzers, or to an automatictape-controlled electrical typewriter.

Here a punched tape carrying holes laid out in accordance with a binarycode equivalent of the values discovered during the tests is needed. InFIGURE 7, the drum 40 can be provided with a series of punch pins on itsperiphery, aligned axially on that surface and located in accordancewith the desired code. These pins can be supplementary to or asubstitute for the regular printing embossments corresponding to digitalfigures. The platen 81 then carries a row of matching holes so that whenthe paper tape is forced against the tips of the punch pins certainholes are produced wherever such pins are placed. Correct alignment ofthe pins and die plate can be insured by the addition of a gear typealignment on the rim of the drum such as at 62 of FIGURE 6, and acorresponding detent centering pawl similar to 66.

What is claimed is:

An electro-mechanical instrument comprising:

(a) a meter element having a main coil movable in response to an appliedenergizing current, a circuit control switch operable by the movablecoil, and a bias coil to set the current value which will be sufficientto cause the main coil to operate the switch;

(b) a plurality of external resistors of fixed values selectivelyinsertable into the circuit of the main coil to establish a staticoperating calibration value of the main coil for operating the switch;

(0) an independent variable resistor in circuit with the bias coil, toprovide a range of dynamic calibrations to the main coil, according tothe position setting of the variable resistor;

(d) means for varying said variable resistor through its full range ofvariation in resistance values to establish arange of calibrations inthe main coil to span the static operating calibration value set up bythe fixed resistors; and

(e) means responsive to operation of the meter switch for displaying thepercentile relation between the dynamic calibration value and thearbitrary static calibration value at the instant of operation of saidmeter switch.

References Cited UNITED STATES PATENTS 2/1950 Rich 324-113 X 102,758,830 8/1956 Bentley.

2,824,926 2/ 1958 Daschke 200-56 X 15 11, 4 pages.

WALTER L. CARLSON, Primary Examiner.

E. L. STOLARUN, Assistant Examiner.

